Since the first public mobile radio systems introduced in the late 1970's and early 1980's, several generations of mobile radio communication systems have evolved in different parts of the world. First generation systems included, for example, the Advanced Mobile Phone System (AMPS) in the United States, Nordic in Scandinavia, Total Access Communications System (TACS) in Great Britain, and Nippon Mobile Telephone System (NAMTS) in Japan. Each of these first generation (1G) systems had similar transmission characteristics such as analog frequency modulation at the radio and digital control of the network. Second generation (2G) systems based on Time Division Multiple Access (TDMA) included Global System for Mobile communications (GSM) which became the standard in Europe followed in the United States by Digital AMPS (DAMPS), the TDMA version of which is sometimes referred to by its standardization name, IS-54. The Japanese second generation system was called Personal Digital Cellular (PDC). Work is currently ongoing in third generation (3G) systems that are based on a Wideband Code Division Multiple Access (WCDMA) air interface. An example of a 3G system is a Universal Mobile Telecommunication System (UMTS). Other air interfaces that can be used to provide third generation services include Enhanced Data rate for GSM Evolution (EDGE) and multicarrier CDMA sometimes referred to as CDMA 2000.
Third generation systems permit backward compatibility with other earlier types of radio systems such as GSM to allow multi-mode user equipments (UEs) to obtain service from both 2G and 3G systems. This requires that the multi-mode UEs and the 2G and 3G infrastructures support an inter-system handover from a cellular system that employs one type of radio access technology (RAT) to another cellular system that employs a different type of radio access technology, e.g., from GSM/TDMA to UMTS/CDMA. Commonly-assigned U.S. patent application Ser. No. 09/286,472, filed on Apr. 6, 1999, and entitled “Inter-System Handover—Generic Handover Mechanism,” describes one mechanism for accomplishing such inter-system handovers, the disclosure of which is incorporated herein by reference.
Although having inter-system handover functionality is a desirable capability to offer to subscribers, network operators also want to control access to such inter-system handover functionality. Indeed, certain subscribers may need to be prevented from accessing certain types of mobile radio communication systems, or even from performing any type of inter-system handover. For example, subscribers who have only paid for GSM service should not normally be able to perform a handover to obtain Wideband CDMA services without paying for those Wideband CDMA services. On the other hand, operators may want to allow inter-system handover for all subscribers in very limited circumstances, such as an emergency call. In addition to subscriber policing functions, network operators want the ability to move subscribers from one radio access technology to another. One example is handing over UMTS subscribers making a speech-only call to a GSM system to free capacity in the UMTS system (designed for multimedia services), while still providing the subscriber the same quality of service for the speech-only call using the less expensive GSM system (designed primarily for speech services).
General handover procedures are specified by the Third Generation Partnership Project (3GPP) in 3GPP 23.009, Version 4.0.0, entitled “Handover Procedures.” A service handover Information Element (IE) is specified for use in instructing a radio access network node, such as a Radio Network Controller (RNC), how to implement inter-system handovers. However, these general procedures are not adequate to properly facilitate desirable operator control of various inter-system handover situations.
When a service handover information element is provided to a decision making node in the target network to which an inter-system handover is requested, that node can determine how to handle the system handover request, including whether to permit the handover. Consider the example situation illustrated in FIG. 1 where a UE is requesting an inter-system handover from a GSM system to a WCDMA/UMTS system (HO#1). The GSM system includes an “anchor” Mobile services Switching Center (MSC) through which the original radio connection with the user equipment is established via a serving Base Station Controller (BSC) and radio Base Station (BS). To request a handover from the GSM system to the WCDMA system, the anchor MSC sends a handover request message over an E-interface to a “non-anchor” MSC in the WCDMA system. That request includes a service handover information element associated with the UE and/or UE connection. The information element is necessary because the non-anchor MSC is not aware of the UE's subscription or the type of call in the UE connection. The non-anchor MSC provides the service handover information element over an Iu interface to the serving RNC that will decide if a subsequent inter-system handover request should be executed. In order to determine if the subsequent inter-system handover is permitted or desired by the network operator, the RNC checks the specific data provided in the service handover information element.
In this example, the UE connection is set up in a GSM system, and the BSC provides the anchor MSC with a “Handover Required” message. The anchor MSC can encapsulate this information or otherwise transfer it over the E-interface to the non-anchor MSC. One problem in this situation is the non-anchor MSC is not a GSM MSC—it is a WCDMA/UMTS MSC using WCDMA/UMTS protocols. Unlike the anchor MSC, the non-anchor cannot interpret the service handover information element based on subscriber information. Nor does it have access to the UE subscription and information about the UE connection, e.g., a normal call, an emergency call, a speech call, a data call, etc. Only the anchor MSC involved in the initial connection setup “knows” the UE subscription and UE connection information. As a result, the non-anchor MSC cannot readily interpret the service handover information element in the GSM-related protocol format. Nor can it easily translate the GSM-based service handover information element into a corresponding WCDMA-based service handover information element that would be understood by the serving RNC which is responsible for determining whether the subsequent handover should be permitted (requested by UE) or promoted (desired by network operator). Although the non-anchor MSC can readily pass the GSM-based service handover information element to another BSC, if the target system was another GSM system, that is not the case here.
A similar problem exists for subsequent inter-system handover requests for the UE connection. Assume the same UE later requests an inter-system handover from the WCDMA/UMTS system back to the same GSM system (or to some other GSM system), as represented by the arrow in the HO#2 shown in FIG. 1. Because the non-anchor MSC only received the WCDMA/UMTS service handover information element, the anchor MSC lacks information necessary to interpret or otherwise translate a WCDMA/UMTS service handover information element into a GSM service handover information element. The problem propagates for each subsequent inter-system handover request. This problem in the non-anchor MSC exists even if an inter-system handover is requested that does not require an inter-MSC handover, i.e., a single, non-anchor MSC supports a BSC node (GSM) and an RNC node (WCDMA/UMTS). This is called an inter-system, intra-MSC handover. That non-anchor MSC does not have the ability to send a GSM service handover information element to the BSC node as well as an WCDMA/UMTS service handover information element to the RNC node depending on what is needed.
As a result, the non-anchor MSC may neither block nor promote inter-system handover to certain radio access technologies based upon a mobile UE subscription. As a result, the administration of inter-system handover based on subscription or call type must be handled from the anchor MSC which complicates administration of the inter-system handover functionality. The present invention overcomes these problems and facilitates operator control over inter-system handover between different types of radio access technologies. Assuming a radio connection has been established between a first mobile radio communications system and a User Equipment (UE) using an anchor node, a request is made for handover of the UE connection to a second mobile radio communications system that includes a non-anchor node. UE handover information is provided to the non-anchor node. The UE handover information includes first radio handover information relating to handover of the connection from the first mobile radio communication system to the second mobile radio communication system and second handover information relating to handover from the second mobile radio communications system to the first mobile radio communications system.
The non-anchor node forwards one of the first and second UE handover information to a radio access network node in the target system that decides whether to permit or initiate a subsequent requested inter-system handover of the connection. The first handover information element is formatted in accordance with a first protocol format employed in the first system, and the second information element is formatted in accordance with a second protocol format employed in the second system. The non-anchor node provides the handover information element in the protocol format recognized by the inter-system handover decision making node. As a result, the radio access network node readily determines from the information element whether the UE subscription and/or type of call warrants an inter-system handover.
The information elements may indicate whether the handover from the first system to the second system is permissible, and whether and handover of the connection in the other direction from the second to first system is permissible. Other more qualified handover conditions may also be provided in the information element, e.g., an indication whether handover to the second system (or the first system) should not be performed unless there are no resources available in the first (second) system.
In one non-limiting, example application, the first and second mobile radio communication systems correspond to GSM-type and UTRAN-type systems. The GSM-type system includes a GSM-supporting MSC coupled to at least one Base Station Controller (BSC) which controls plural radio base stations. The UTRAN-type system includes a UTRAN-supporting MSC coupled to at least one Radio Network Controller (RNC) which controls plural radio base stations. Assuming a radio connection is established between the GSM system and a user equipment (UE) using an anchor MSC, the anchor MSC processes an inter-system handover request for the UE connection from BSC to the UTRAN system. The anchor MSC provides service handover information for the UE to the non-anchor MSC in the UTRAN system.
The service handover information includes a GSM-formatted handover information element and a UTRAN-formatted handover information element. The GSM handover information element relates to handover of the connection from the GSM to the UTRAN system. The UTRAN information element relates to handover from the UTRAN to the GSM system.
In this way, the non-anchor MSC in the UTRAN network has service handover information for that UE subscription and connection formatted both for ready communication with the RNC node in the UTRAN system and for ready communication with a BSC node in the GSM system (or some other GSM system). With this properly-formatted service handover information, the non-anchor MSC can intelligently facilitate subsequent inter-system handover requests. For subsequent GSM-to-UTRAN handover requests, the non-anchor MSC can provide a UTRAN-formatted service handover information element to an RNC. For subsequent UTRAN-to-GSM handover requests, the non-anchor MSC can provide a GSM-formatted service handover information element to a BSC.